Nowadays the use of laundry washing machines, both “simple” laundry washing machines (i.e. laundry washing machines which can only wash and rinse laundry) and washing-drying machines (i.e. laundry washing machines which can also dry laundry), is widespread.
In the present description the term “laundry washing machine” will refer to both simple laundry washing machines and laundry washing-drying machines.
Laundry washing machines generally comprise an external casing provided with a washing tub inside which there is a rotatable perforated drum in which the laundry is placed.
A loading/unloading door ensures access to the tub and the drum.
Laundry washing machines typically comprise a detergent supply unit and a water inlet circuit for the introduction of water and washing/rinsing products (i.e. detergent, softener, etc.) into the tub.
Known laundry washing machines are also provided with water draining devices that may operate both during the initial phases of the washing cycle and at the end of the same to drain the dirty water.
In particular, a known complete washing cycle typically includes a first laundry wetting phase with addition of the washing detergent, a second washing phase during which the tub is rotated and the water contained therein is heated to predetermined temperature values based on the washing programme selected by the user, and a final rinsing and spinning phase.
According to the known technique, the initial wetting phase includes successive steps intended to determine the quantity of water necessary for wetting the laundry completely and to introduce said water in the tub, as well as to proportion the detergent correctly according to the type of laundry to be washed. A wetting method is disclosed in document EP1961854. In this document the wetting phase includes first the determination of the load in terms of weight of the laundry, in order to establish the minimum quantity of washing water to be introduced in the tub.
Successively this quantity of washing water, consisting of water and detergent, is introduced in the tub.
Then further washing water is introduced until it is detected that a minimum level of washing water has been reached inside the tub, while at the same time the laundry is wetted.
The minimum level depends on the type of programme selected and on the quantity and type of laundry.
Suitable level sensors detect that the minimum level has been reached.
Once the introduction of washing water in the tub has been interrupted, the washing water that remains in the hollow space between the tub and the drum is drained and reintroduced in the tub through a special hydraulic circuit that pumps the washing water from the bottom of the tub to a nozzle arranged in the upper part of the tub.
The washing water that is reintroduced further wets the laundry.
Successively, the quantity of washing water present on the bottom of the tub is measured and further water is added until reaching a minimum level, so as to cover the heating means consisting of a resistor positioned at the base of the tub. Then the cycle continues through the control of both the level of the water present inside the tub and the temperature reached by the water itself, so as to guarantee that the washing cycle is carried out at the correct temperature according to the set programme.
However, the method of wetting the laundry above described belonging to the known art pose some drawbacks.
A first drawback posed by this known technique is constituted by the fact that the wetting phase lasts a long time.
A further drawback is represented by the fact that perfect and homogeneous wetting of the laundry is not guaranteed.
A further drawback lies in that part of the detergent is mixed with the washing water that fills the hollow space, said water being in excess of the quantity of water that is sufficient to wash the laundry and to wet it completely.
The object of the present invention is therefore to overcome the drawbacks posed by the known technique.
It is a first object of the invention to implement a wetting method for a washing cycle of a laundry washing machine that is quicker than the methods of known type.
It is a further object of the invention to implement a wetting method that makes it possible to obtain more efficient wetting of the laundry compared to the known technique.
It is another object of the invention to implement a wetting method that makes it possible to optimise the dosage of the detergent and to reduce the quantity of detergent used compared to the known technique.